Milliamps to Amps
Convert milliamps to amps for power supply ratings, charger specs, fuse selection and current draw calculations. 1000 mA = 1 A, reference table with common values.
Last updated: May 2026
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Why milliamps and amps need explicit conversion
Component and sensor specs are typically in milliamps; power supply ratings, fuse sizes and wiring capacity are in amps. Mixing scales without converting is how circuits get over-fused or under-specified. A 500 mA fuse protects a circuit drawing up to 0.5 A, if you read the label in milliamps and compare against an amp-rated limit, the numbers don't directly compare.
The formula is amps = milliamps ÷ 1000. An ATmega microcontroller at 80 mA total system draw is 0.08 A. Three USB devices at 500 mA each sum to 1500 mA = 1.5 A, the figure needed to size a power supply or cable.
When you need this conversion
- Power supply sizing: add all mA loads, convert total to A, match against supply rating
- Fuse selection: fuse ratings are in amps; if loads are in mA, convert before comparing
- Wire gauge calculation: AWG and mm² tables use amps, not milliamps
Quick reference
| Milliamps | Amps |
|---|---|
| 20 mA | 0.02 A (standard LED) |
| 100 mA | 0.1 A |
| 500 mA | 0.5 A (USB 2.0 max) |
| 1000 mA | 1 A |
| 2000 mA | 2 A (USB-A charger) |
Related tools
USB current standards and common load draws
USB standards define the maximum current a port is allowed to supply; the device negotiates its actual draw within that ceiling. These limits matter when deciding whether a charger can power multiple devices simultaneously or when sizing a power bank's output current.
| Standard | Max current (mA) | Max current (A) | Max power |
|---|---|---|---|
| USB 2.0 (low power) | 100 mA | 0.1 A | 0.5 W at 5 V |
| USB 2.0 (high power) | 500 mA | 0.5 A | 2.5 W at 5 V |
| USB 3.0 / USB-A charger | 900-2000 mA | 0.9-2 A | 4.5-10 W at 5 V |
| USB-C (standard) | 3000 mA | 3 A | 15 W at 5 V |
| USB-C Power Delivery | up to 5000 mA | up to 5 A | up to 100 W (20 V x 5 A) |
| Standard 5 mm LED | 20 mA | 0.02 A | Typical single-LED resistor target |
| WS2812B LED (per LED, max) | 60 mA | 0.06 A | 3 channels x 20 mA each |
To size a power supply for multiple devices: add all load currents in mA, convert the total to amps, then add 20% headroom. For example, four USB devices at 500 mA each equals 2000 mA = 2 A; with headroom, a 2.5 A supply is the minimum safe choice.
For LED strips, multiply the per-LED draw by the total LED count. A 60-LED/m strip of WS2812B LEDs at full white draws 60 x 60 mA = 3600 mA = 3.6 A per metre at maximum brightness. Driving at 50% brightness roughly halves that.
Frequently Asked Questions
When do I need to convert milliamps to amps?
Power supply design uses amps for total current budgets, even if individual loads are measured in milliamps. Sum all load currents in mA, then convert to A to select the correct fuse rating, wiring gauge and regulator current specification.
What is a typical microcontroller system's total current draw in amps?
A bare ATmega328 at 5 V draws around 15 mA (0.015 A) at 16 MHz. Add LEDs, sensors and communication modules and total system draw commonly reaches 100-300 mA (0.1-0.3 A). That is the figure you use to size the power supply and battery pack.
How accurate does this conversion need to be for bench work?
The factor is exact: 1 mA = 0.001 A. Precision is rarely the issue, the risk is forgetting to convert before selecting a fuse or regulator. A 500 mA fuse is only 0.5 A; if your load peaks at 600 mA, that fuse will blow even though the label looks large enough when reading it in milliamps.
How many mA does an LED strip draw per metre?
It depends on the LED type and colour. A common WS2812B strip (60 LEDs per metre) draws up to 60 mA per LED at full white, so 3600 mA (3.6 A) per metre at maximum brightness. Reduce brightness to 50% and current roughly halves. For single-colour strips like 5050 SMD, a 60-LED/m strip typically draws around 720 mA per metre at full output. Always measure from the datasheet, not the listing title, and power strips from both ends for runs longer than 3 metres to avoid a voltage drop that causes colour shift at the far end.
What is the difference between mAh and mA on a battery or power bank?
mAh (milliamp-hours) is capacity: how much total charge the battery holds. mA (milliamps) is current: how fast that charge flows. A 10,000 mAh power bank delivering 2000 mA to a phone lasts about 5 hours before it is empty (10,000 / 2000 = 5 hours), ignoring conversion losses. The output current rating on the power bank tells you the maximum mA it can supply simultaneously, not the speed at which it will drain. Choosing a power bank with a 3 A output port matters when the device you are charging requires 3 A to fast-charge.